cslect()

logical function cslect

(

complex

z

)

CSLECT

Purpose:

!>
!> CSLECT returns .TRUE. if the eigenvalue Z is to be selected,
!> otherwise it returns .FALSE.
!> It is used by CCHK41 to test if CGEES successfully sorts eigenvalues,
!> and by CCHK43 to test if CGEESX successfully sorts eigenvalues.
!>
!> The common block /SSLCT/ controls how eigenvalues are selected.
!> If SELOPT = 0, then CSLECT return .TRUE. when real(Z) is less than
!> zero, and .FALSE. otherwise.
!> If SELOPT is at least 1, CSLECT returns SELVAL(SELOPT) and adds 1
!> to SELOPT, cycling back to 1 at SELMAX.
!> 

Parameters

[in]

Z

!> Z is COMPLEX !> The eigenvalue Z. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 55 of file cslect.f.

*
*  -- LAPACK test routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      COMPLEX            Z
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      REAL               ZERO
      parameter( zero = 0.0e0 )
*     ..
*     .. Local Scalars ..
      INTEGER            I
      REAL               RMIN, X
*     ..
*     .. Scalars in Common ..
      INTEGER            SELDIM, SELOPT
*     ..
*     .. Arrays in Common ..
      LOGICAL            SELVAL( 20 )
      REAL               SELWI( 20 ), SELWR( 20 )
*     ..
*     .. Common blocks ..
      COMMON             / sslct / selopt, seldim, selval, selwr, selwi
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          abs, cmplx, real
*     ..
*     .. Executable Statements ..
*
      IF( selopt.EQ.0 ) THEN
         cslect = ( real( z ).LT.zero )
      ELSE
         rmin = abs( z-cmplx( selwr( 1 ), selwi( 1 ) ) )
         cslect = selval( 1 )
         DO 10 i = 2, seldim
            x = abs( z-cmplx( selwr( i ), selwi( i ) ) )
            IF( x.LE.rmin ) THEN
               rmin = x
               cslect = selval( i )
            END IF
   10    CONTINUE
      END IF
      RETURN
*
*     End of CSLECT
*

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